This invention relates generally to pneumatically powered mechanisms and particularly to pneumatically powered mechanisms for use in seat cushions suitable for use in chairs and vehicle and airplane seats. Still more particularly, this invention relates to mechanisms for controlling the fluid pressure in a seat cushion or seat bolster bladder system.
Various types of inflatable seat and cushion constructions are currently employed to provide comfortable support for various sections of the body such as the lower back. To vary the amount of support to the lower back or to other parts of the seat occupant's body, inflatable/deflatable bladders are placed externally to the resilient foam of the cushion and connected to a manually operated pump and vent valve system or to an electric powered compressor and an electropneumatic switch assembly/valve system. Such bladders may have one or more chambers that may be selectively inflated or deflated.
Many modern automobile seats have side bolsters that include inflatable/deflatable bladders. These side bolsters may be arranged to fit against the hips or shoulders of a person sitting in the seat. The side bolsters prevent the seat occupant from sliding laterally when the automobile turns a corner or goes around a curve. Previous inflatable bladder arrangement for have allowed fluid communication between the bladders on opposite sides of the seat. Therefore, if the seat occupant exerts a force on the left shoulder bolster, for example, the resulting pressure differential causes gas to flow from the left bolster bladder to the right bolster bladder. This gas flow is undesirable in seats designed for applications where firm support is required.